Hi, thanks for posting.
At the moment, there isn't any built in feature that will let you do this. However, the new config engine currently in development is expected to allow you to set config settings at different levels (i.e. global, solution, project) and have them inherit downwards.
You might find it useful to create a shared build file imported by all your projects in this solution. You can then use this file for creating your own custom targets, or overriding build properties in a global fashion. In my experience, a solution-wide import used by all projects is one of those things that tends to become useful in all sorts of unexpected ways as you continue development.